Which one of the following elements has a ground state electronic configuration of [Ar] 4s2 3d10 4p3?
A) Se
B) Cr
C) Br
D) Ga
The correct answer and explanation is :
The correct answer is A) Se (Selenium).
Explanation:
To determine the element with the given ground state electronic configuration of [Ar] 4s² 3d¹⁰ 4p³, let’s break down the electron configuration and match it with the periodic table.
1. Understanding the Notation:
- [Ar] refers to the electron configuration of argon, which is a noble gas with the atomic number 18. Therefore, the configuration starts with argon’s electrons and proceeds from there.
- The configuration 4s² 3d¹⁰ 4p³ describes additional electrons after argon:
- 4s² indicates two electrons in the 4s orbital.
- 3d¹⁰ indicates ten electrons in the 3d orbital.
- 4p³ indicates three electrons in the 4p orbital.
2. Total Number of Electrons:
- Argon (Ar) has 18 electrons, so starting from Ar, we add the electrons from the 4s², 3d¹⁰, and 4p³ orbitals:
- 18 (from Ar) + 2 (from 4s²) + 10 (from 3d¹⁰) + 3 (from 4p³) = 33 electrons.
- An element with 33 electrons is Selenium (Se), which has an atomic number of 34. Therefore, its full electron configuration is: [Ar] 4s² 3d¹⁰ 4p³.
3. Periodic Table Position:
- Selenium (Se) is located in group 16 of the periodic table, which is known as the chalcogens. The electronic configuration of Se confirms it is in this group because it ends with 4p³, where it has three electrons in the p-block.
4. Why Other Options Are Incorrect:
- B) Cr (Chromium) has an electron configuration of [Ar] 4s¹ 3d⁵, which is different from the given configuration.
- C) Br (Bromine) has an electron configuration of [Ar] 4s² 3d¹⁰ 4p⁵, which shows 5 electrons in the 4p orbital, not 3.
- D) Ga (Gallium) has an electron configuration of [Ar] 4s² 3d¹⁰ 4p¹, which ends with a 4p¹ configuration, not 4p³.
Thus, the element that has the ground state electron configuration [Ar] 4s² 3d¹⁰ 4p³ is Selenium (Se).